US Clean Air Act saved more lives than thought: study

The US Environmental Protection Agency's (EPA) Clean Air Act and amendments to address the health effects of particulate matter may have significantly reduced organic aerosols and saved more lives than previously estimated, a study has found.
Particulate matter is responsible for thousands of premature deaths in the US each year.
New research from Massachusetts Institute of Technology (MIT) in the US proposes that the EPA's legislation may have saved even more lives than initially reported.
"In the US, the number of premature deaths associated with exposure to outdoor particulate matter exceeds the number of car accident fatalities every year," said Colette Heald, associate professor at MIT.

"This highlights the vital role that the EPA plays in reducing the exposure of people living in the US to harmful pollutants," said Heald.
The EPA's 1970 Clean Air Act and amendments in 1990 address the health effects of particulate matter, specifically by regulating emissions of air pollutants and promoting research into cleaner alternatives.

In 2011 the EPA announced that the legislation was responsible for a considerable decrease in particulate matter in the atmosphere, estimating that over 100,000 lives were saved every year from 2000 to 2010.
However, the report did not consider organic aerosol, a major component of atmospheric particulate matter, to be a large contributor to the decline in particulate matter during this period.

Organic aerosol is emitted directly from fossil fuel combustion (eg vehicles), residential burning, and wildfires but is also chemically produced in the atmosphere from the oxidation of both natural and anthropogenically emitted hydrocarbons.
Researchers looked at surface measurements of organic aerosol from across the United States from 1990 to 2012, creating a comprehensive picture of organic aerosol in the US.
The MIT researchers found a more dramatic decline in organic aerosol across the US than previously reported, which may account for more lives saved than the EPA anticipated.
Their work showed that these changes are likely due to human behaviors.

"The EPA report showed a very large impact from the decline in particulate matter, but we were surprised to see a very little change in the organic aerosol concentration in their estimates," said David Ridley, a research scientist at MIT.
"The observations suggest that the decrease in organic aerosol had been six times larger than estimated between 2000 and 2010 in the EPA report," said Ridley.